(Trichloromethyl)pyridine compounds, such as nitrapyrin, have been used as nitrification inhibitors in combination with fertilizers as described in U.S. Pat. No. 3,135,594, which is herein incorporated by reference. These compounds maintain applied ammonium nitrogen in the ammonium form (stabilized nitrogen), which enhances crop performance. It would be desirable to broadly apply these compounds with nitrogenous fertilizer at sowing time, but due to potential volatility losses, these application methods are generally unsatisfactory. In addition nitrapyrin has been added to anhydrous ammonia, which by default must be injected into the soil.
Other nitrapyrin formulations have been applied to the surface of the soil, but must either be incorporated mechanically, or watered into the soil within 8 hours after application to overcome volatility losses. Finally, rapid or dump release capsule formulations of nitrapyrin encapsulated with lignin sulfonates have also been disclosed in U.S. Pat. No. 4,746,513, which is incorporated herein by reference. However, although the release of nitrapyrin is delayed by the encapsulation, the capsules release all of the nitrapyrin upon contact with moisture, exhibiting the same stability and volatility disadvantages of the prior application methods. Additionally, these formulations are difficult and costly to produce and cannot be used with liquid urea ammonium nitrate (“UAN”) fertilizers.
Polycondensation encapsulation, as disclosed in U.S. Pat. No. 5,925,464, has been used to encapsulate agriculturally active ingredients, particularly to enhance handling safety and storage stability of the active ingredient by using polyurethane rather than polyurea encapsulants.
However, there remains a need to deliver nitrification inhibitors such as (trichloromethyl)pyridines, having greater long term stability in the field environment, while maintaining the level of efficacy of unencapsulated inhibitors.